1. Field of the Invention
The present invention relates to conductive paste, a photovoltaic apparatus and a method of manufacturing a photovoltaic apparatus, and more particularly, it relates to conductive paste prepared by dispersing a conductive material into binder resin, a photovoltaic apparatus including an electrode prepared from this conductive paste and a method of manufacturing this photovoltaic apparatus.
2. Description of the Background Art
Conductive paste prepared by dispersing particles of silver (Ag) serving as a conductive material into binder resin is known in general. A photovoltaic apparatus including a collector prepared from the aforementioned conductive paste is also known in general. For example, Japanese Patent Laying-Open No. 2002-76398 discloses such a photovoltaic apparatus.
Japanese Patent Laying-Open No. 2002-76398 discloses a photovoltaic apparatus including an interdigital collector, having a finger portion and a bus bar portion, formed on a prescribed region of a translucent conductive film. The finger portion of the collector has a function of collecting currents, while the bus bar portion has a function of aggregating the currents collected in the finger portion. The collector of the conventional photovoltaic apparatus disclosed in Japanese Patent Laying-Open No. 2002-76398 is prepared by printing conductive paste on the prescribed region of the translucent conductive film by screen printing and thereafter hardening the printed conductive paste.
In the aforementioned conventional photovoltaic apparatus including the collector, it is important to reduce the size of a light blocking region (region formed with the collector) by narrowing the finger portion of the collector, in order to increase the quantity of incident light. Therefore, the conductive paste printed by screen printing must be inhibited from spreading in the transverse direction (cross direction). In order to inhibit the printed conductive paste from spreading in the transverse direction (cross direction), the viscosity of the conductive paste may be controlled by adjusting the compound ratio between binder resin and a solvent constituting the conductive paste, for example. More specifically, the viscosity of the conductive paste is increased when the quantity of the solvent constituting the conductive paste is reduced, whereby the printed conductive paste can be inhibited from spreading in the transverse direction (cross direction).
However, the method of inhibiting the printed conductive paste from spreading in the transverse direction (cross direction) by reducing the quantity of the solvent constituting the conductive paste has the following inconvenience: When the viscosity of the conductive paste printed by screen printing is increased by reducing the quantity of the solvent, the quantity of the conductive paste injected from an opening of a screen printing plate is so reduced that it is difficult to increase the height of the printed conductive paste. Therefore, the ratio of a nonconductive component (binder resin) in the conductive paste is increased due to the reduced quantity of the solvent, and the sectional area of the printed paste is reduced due to the small height. Consequently, the sectional area of an electrode prepared from the conductive paste is reduced to disadvantageously increase the resistance thereof, although this electrode can be narrowed.